Sam, I agree with Lou on the size of the alternator. I don't think you should need a "monster" unit. I don't remember what alternator mount you have.
If you are using a stock slant six "cast" mount, why not use the Nippondenso unit from a 88 or 89 dodge truck. If you cut 1/4 inch off the front of the mount It is a bolt on deal, and has approx 100 amp output.
Just make sure to get the alternator with a "V" belt pulley (I don't remember whether that is the 88 or 89).
I run them on my race car, with twin electric fuel pumps, Electric fan and water pump, MSD ign, nitrous bottle heater, and lights.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I am a minimalist. If it works well with 45 A, then I will try to use a smaller one and see if that works well. So far, that has been more than enough. However, these cars do not have AC, huge fans, etc... Momentary voltage drops have had no ill effects on my cars so far.

For my turbo install, I wanted to try w/o intercooler first for the simplicity. So far, I'm at 330-340 HP calculated from dragstrip runs. I did have to go to water/meth inj for reliability, but that is still simpler than running intercooler piping and cutting things up.

I just don't think Sam's problem is that the alternator is too small. I am not sure, but that is my feeling.

Lou

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Home of Slant6-powered fun machines since 1988

What else would cause the voltage to drop 1 volt at idle over 20 minutes? It went from 13.5 to 12.5. I honestly do not see how a larger output alternator adds to complexity. It is not like am adding circuits or wires.

BTW thanks for the thoughts. I appreciate the thoughtful contributions, and the forum for chewing on an idea. That is what this site should be all about.

Sam

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The later chrysler / nippondenso 90 (some 110a?) units is an alternative - but he already has a gm unit in there, the swap to a cs144 would be simple and allow for extra headroom especially at idle.

Sam I doubt the outside of the box would say that. You'd have to go purely on looks. The piece of paper / tag etc within the box where they test the output may say it.

Stock CS144 style regulators need 2 connections. One is a "sense" wire - it regulates its output according to whatever voltage is present on this wire. I just loop it back to the output stud, or you can run it to a fuse box or main junction point. The other is what "activates" the charging - you can either run it through a resistor and/or light (with other side connected to switched power) to show you if its charging or not.

Sam the quality power units are nice (hand built, onshore etc) so if you don't mind spending more on them go for it.

Oooo... just found these - direct bolt in for stock unit - pricy, but zero install hassle and still delivers mondo current. If I didn't already have my gm units I would be all over it.

I don't see that as a problem, If your electrical system is that sensitive to voltage flucuations, I think you have a different problem. Very few cars will charge the battery at idle, with a full electrical load applied. Plus 20 minutes is a long time to idle. Once you are above idle the higher the output rating of the alternator, the faster (shorter period of time)the alternator will replace the power "borrowed" from the battery.
Adding a larger output alternator does not necessarlly add to the complexity, but does mean more money spent that is not solving your "real" problem.

Sam, I really am not that familia with your set up, but take my barracuda for example. With the stock 39 amp alternator, I would eventually wind up with a dead battery. I don't remember the exact power drain of each component, but, electric fuel pumps(2) 8 amps ea. electric fan/water pump 20 amps, bottle heater 30 amps, MSD 8 amps, lights 10 amps, total
84 amps, Then there is the power used to start the engine. and move the car up in the staging lanes. The stock alternator could not put enough money (amps) back in the bank(battery) that all the devices borrowed from the bank(battery). Eventually the bank didn't have any money left (dead battery). The larger alternator could Put more back (more and larger deposits into the bank) into the battery over a shorter period of time to keep the battery charged up. I don't even use the alternator when at full throttle (field cutout switch). But the system charges at a high rate, when driveing through the pits, burn out, staging, return road, etc.
I don't know if this is making any sense to you.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

You don't see 12.5v as a problem on a street car? What if you get stuck in stop and go traffic for an extended period? That can be well more then 20 min. You won't be revving high or long enough to give the alt a chance to put any money back into the bank. Maybe expecting full charge at idle is not realistic, but dipping into the battery (anything below 12.6) on a street car just doesn't seem wise.

What's your idle speed?

Just raising it may fix the problem.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

It won't. From a cold start he said his voltage is fine.

I'm thinking the temperature compensation in the votage regulator may be bad. I don't care for 1-wire alternators. I would much rather have the regulator sense votage nearer the load or battery.

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Joshua

That's certainly a possibility I didn't think of - The specs can probably be had if we knew the exact regulator part number. Replacing the regulator within would be easy enough to do if you didn't mind tinkering. You can convert it back to non-one wire operation at the same time. Time consuming experiment but could be fun.

I'm not a fan of one wires either anymore. You have to rev them to a specific rpm before they self energize and begin charging. If it drops below a certain rpm its output goes to 0. With the standard config at least you get a minor amount of output at low rpms.

There is no real reason NOT to use a larger alternator, EXCEPT for the chance of smoking wires in a system that might not be up to those high currents.

Hope you are making progress,

Lou

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Home of Slant6-powered fun machines since 1988

Just reading, absorbing and thinking. This has been quite educational. I assume others are learning from this discussion as well. I thought the purpose of the voltage regulator was to keep from smoking things. Aren't they supposed to supply only what is needed, up until they hit their max capacity?. And lower voltage increases the amps which increases the heat, if I recall my basic electricity stuff correctly. So it would seem a too-small alternator is MORE likely to toast something.

It idles between 850 and 900.

Sam

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Too small an alternator (if you draw excess current then which it can supply) will make it eventually self destruct - running at full tilt continuously. If the alternator is capable of supplying the current demand but the wiring is too small to move the current produced, the wires themselves will go poof (but alternator itself will be fine).

If I understand this correctly,the would be the wires and not the alternator. So the first step is to make sure the wires can handle the load. I really need that inductive ammeter. My kids were planning on getting it for me for my birthday, which was the 21st of September, but so far they have been too busy. You hate to nag someone to get you a present.

Charlie, I think the EFI stuff, especially where ignition control is concerned, is much more sensitive to voltage fluctuations. Being fundamentally old school in the past, I never paid much attention to this in the past. This is new for me, and I want to make sure this issue is not part of any problem in the future.

Now that I have said that, I realize I became aware of the importance of voltage when I switched to electronic ignition from point. The car began running worse, not better. It seems the old 40 amp alternator, and old corroded wires were fine for a points distributor, but not for the electronic Orange box. Once I upgraded the alternator and replaced the old corroded connections and wires, MPG went from 13 to 18. Eventually it went to 22 with other modifications such as dual exhaust and 2 bbl carb. But the voltage was a big deal to the electronics. EFI with ignition control seems to be orders of magnitude more sensative to this issue.

Sam

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